This page contains information comparing both of the implementations made by Mosaic5G/OpenAirInterface in order to emulate a near-RT RIC. The FlexRAN as already been discontinued, now being the FlexRIC the only available option.

The FlexRIC is a component of the OpenAirInterface project → with the objective of providing an ecosystem of open source 4G/5G service platforms, towards Open RAN and Open CN: openness and interoperability between equipment from different vendors.

FlexRIC follows the Mosaic5G design principles to be multi-RAT, multi-vendor and multi-service.

💡 Flexible RIC (RAN Inteligent controller) and E2 Agent SDK

The RIC is a central component in the O-RAN architecture. It is designed to bring flexibility to the control of the Radio Access Network (RAN). So FlexRIC is designed in such a way that developers and network operators can create custom software-defined RAN controllers.

The E2 Agent SDK is a Software Development Kit designed to facilitate the development of agents that use the E2 interface in the O-RAN architecture:

💡 E2 Interface: standard connection that enables communication between the RIC and the RAN hardware (gNodeBs or eNodeBs).

Also, the RIC uses this E2 interface to monitor and control the RAN in real-time.

Additionally, we have the FlexCN, a separate component but with the same principles: SD-CN controller.

Features by component and per-service model:

• KPM (Key Performance Metric): This metric refers to key performance parameters measured in cellular networks, such as throughput, latency, or packet loss.
• RC (Radio Controller): The software component responsible for managing radio resources in the network, including frequency spectrum allocation and transmission power.
• RLC (Radio Link Control): A protocol in the radio control layer that is responsible for organizing reliable data transmission between base stations (BS) and user devices (UE).
• PDCP (Packet Data Convergence Protocol): A protocol in the packet datagram protocol layer responsible for data compression and decompression, as well as providing security functions in mobile networks.
• MAC (Medium Access Control): A protocol in the medium access control layer that regulates access to physical channels in cellular networks, including time and frequency allocation.
• SLICE: This term refers to the concept of network slicing in 5G networks, where the network infrastructure can be divided into virtual chunks that can be organized independently to support different types of services with different qualities.
• TC (Traffic Classifier): A component used to classify network traffic based on certain types or characteristics, such as application or service type.
• GTP (GPRS Tunneling Protocol): A protocol used to transmit data packet traffic between nodes in a mobile network, such as between gateway nodes and base nodes.

These are some of the RAN monitoring service models (examples):

Also, FlexRIC from a memory and storage stanpoint:

• Fine-grained monitoring (thanks to advanced service models)
• Slicing control, traffic control, mobility control
• Network store
• Realtime down to sub ms
• Extendable and plug-and-play service models
• Command line interface application
• Built using C/C++ and Python with support for x64 Linux Systems

As we already know, SDN or Software Defined Networking is one of the key technologies in 5G and evolving mobile networks. These SDN principals are normally accompanied by:

• Separation of control plane and data plane via a well defined API
• Support for real-time control (essential to many RAN operations)
• Easily implement new control functions
• Dynamically adapt the control scheme to the network requirements

💡 Essentially, what we look forward is a platform that can perform all these operations

The FlexRAN platform, from the Mosaic5G platform is made up of two main components: FlexRAN Control Plane & FlexRAN Agent API.

The FlexRAN control is composed by a Master Controller connected to a number of FlexRAN Agents - one connected to each eNodeB. The FlexRAN Agent API acts as a southbound API → interface that connects and communicates with components that are lower in the hierarchy.

Note: the Master Controller can also be denominated as Real-Time Controller?

For the communication between the master controller and the agents we have the FlexRAN Protocol.

In one direction, the agent sends relevant messages to the master with eNodeB statistics, configurations and events, while in the other direction the master can issue appropriate control commands that define the operation of the agents.

On top, we have a northbound API which allows RAN Apps to control and modify the state of underlying components such as eNodeBs and UEs based on statistics and events gathered from the eNodeBs in the FlexRAN control plane.

Flow of operations:

• FlexRAN Agent: This component collects statistics and notifications (protocol messages) from the underlying network or RAN. These messages contain essential data about the network's current state.
• RIB Updater: The FlexRAN Agent sends the collected stats and notifications to the RIB Updater. The RIB Updater processes these inputs and generates the necessary updates for the RIB.
• RIB (Routing Information Base): The RIB stores the current state and configuration of the network. The RIB Updater makes RIB update calls to modify the RIB's content based on the latest data from the FlexRAN Agent.
• Events Notification Service: This service monitors the RIB and responds to any changes or queries made by applications. It is responsible for notifying applications about significant events or changes in the RIB.
• Application: The application queries the RIB to get the current state or configuration of the network. It relies on the Events Notification Service to stay updated on any changes to the RIB that might affect its operation.

RAN control applications can be developed both on the top of the RAN runtime and RTC SDK allowing to monitor, control and coordinate the state of RAN infrastructure. Such applications could vary from soft real-time application including monitoring that obtain statistics reporting to more sophisticated distributed applications that modify the state of the RAN in real-time (e.g. MAC scheduler). All the produced RAN data and APIs are open to be consumed by 3rd parties.

• Plug & Play control apps
  • SDK for App-to-App and App-to-RAN
• FlexRAN Master Controller
  • Top level controller/orchestrator
  • eNB/UE state and resources
• FlexRAN Runtime
  • Abstraction and programmability of network functions
  • Extendable RAN APIs
  • Virtualized resources and states
  • Local controller
  • Support for heterogeneous deployments
• FlexRAN Protocol
  • Statistics
  • Configurations
  • Commands
  • Event Trigger
  • Control delegation

• Control and data plane separation
• Centralized & real-time control: control plane is centralized which simplifies coordination among BS
• Virtualized Control Functions
• Control Delegation & policy reconfiguration: dynamic delegation of control functions and real time reconfiguration of their behavior - also can be implemented using non real time configurations and operations
• User Equipment (UE) Transparency: full transparency to the user equipment ensuring compatibility
• Support of RAN, Content and Device/Provider optimization use cases
• Built using C++ with support for x64 Linux Systems (Master Controller); C for the agent.

Protocol API:

This part of the documentation refers to the xApps found in FlexRIC branch dev, up to commit no a358954c12dd009538473dd16554fa62b8835db7.

• xapp_kpm_rc
• xapp_gtp_mac_rlc_pdcp_moni
• xapp_kpm_moni
• xapp_slice_moni
• tc_all
• tc_codel
• tc_enc
• tc_partition
• tc_segregate
• tc_shaper

These are the tables generated by the xApps:

• GTP_NGUT
• KPM_MeasRecord
• PDCP_bearer
• SLICE
• KPM_LabelInfo
• MAC_UE
• RLC_bearer
• UE_SLICE

• Tunnels GTP-U between the gNB & UPF**

Field	My Description (old)	According to the Standard
tstamp	Measurement timestamp.	Encoded in the same format as the 64-bit timestamp format as defined in clause 6 of IETF RFC 5905 [13].
ngran_node	ID of the gNB node (gNB CU or DU).
mcc, mnc	Mobile Country Code and Mobile Network Code.	Mobile Country Code & Mobile Network Code
mnc_digit_len	Number of digits in the MNC (e.g., 2 or 3).
nb_id	ID of the base station node (gNB).
cu_du_id	Textual identifier of the CU/DU.
teidgnb	TEID on the gNB side.	Tunnel ID from UPF
rnti	UE ID (Radio Network Temporary Identifier).	This represents a temporary UE Identifier in a cell in a Radio Network.
qfi	QoS Flow Identifier.	QoS Flow Identifier (QFI) — This IE identifies a QoS flow within a PDU Session.
teidupf	TEID assigned by the UPF.	Tunnel ID from UPF

• KPM measures records

Field	My Description (old)	According to the Standard
tstamp	Measurement timestamp.	Encoded in the same format as the 64-bit timestamp format as defined in clause 6 of IETF RFC 5905 [13].
ngran_node	ID of the gNB node (gNB CU or DU).
mcc, mnc	Mobile Country Code and Mobile Network Code.	Mobile Country Code & Mobile Network Code
mnc_digit_len	Number of digits in the MNC (e.g., 2 or 3).
nb_id	ID of the base station node (gNB).
cu_du_id	Textual identifier of the CU/DU.
incompleteFlag	TEID on the gNB side.
val	UE ID (Radio Network Temporary Identifier).

• Metrics from PDCP Layer

Field	My Description (old)	According to the Standard
tstamp	Measurement timestamp.	Encoded in the same format as the 64-bit timestamp format as defined in clause 6 of IETF RFC 5905 [13].
ngran_node	ID of the gNB node (gNB CU or DU).
mcc, mnc	Mobile Country Code and Mobile Network Code.	Mobile Country Code & Mobile Network Code
mnc_digit_len	Number of digits in the MNC (e.g., 2 or 3).
nb_id	ID of the base station node (gNB).
cu_du_id	Textual identifier of the CU/DU.
txpdu_pkts	Transmitted data packet (PDU) metrics.	Aggregated number of transmitted RLC PDUs
txpdu_bytes	Transmitted data packet (PDU) metrics.	Aggregated amount of transmitted bytes in RLC PDUs
txpdu_sn	Sequence Number of the last transmitted PDU.	Current sequence number of last TX packet (or TX_NEXT)
rxpdu_pkts	Received data packet (PDU) metrics.	Aggregated number of received RLC PDUs
rxpdu_bytes	Received data packet (PDU) metrics.	Amount of bytes received by the RLC
rxpdu_sn	Sequence Number of the last received PDU.
rxpdu_oo_pkts	Out-of-order packets.	Aggregated amount of out-of-order RX packets (or RX_REORD)
rxpdu_oo_bytes	Out-of-order packets.	Aggregated number of out-of-order RX bytes
rxpdu_dd_pkts	Duplicates discarded.	Aggregated number of RX packets dropped or discarded by the RLC
rxpdu_dd_bytes	Duplicates discarded.	Aggregated amount of RX bytes dropped or discarded by the RLC
rxpdu_ro_count	Rollover count of SNs.	This state variable indicates the COUNT value following the COUNT value associated with the PDCP Data PDU which triggered t-Reordering. (RX_REORD)
txsdu_pkts	SDU (Service Data Unit) metrics.	Number of SDUs delivered
rxsdu_bytes	SDU (Service Data Unit) metrics.	Number of SDU bytes successfully received so far (counter)
rnti	UE ID (Radio Network Temporary Identifier).	This represents a temporary UE Identifier in a cell in a Radio Network.
mode	Mode (AM, UM, etc.)	0: RLC AM; 1: RLC UM; 2: RLC TM
rbid	Radio bearer ID.	Radio Bearer Identification — refers to the unique identification assigned to each radio bearer in the network

• Info about network slices configured in the node

Field	My Description (old)	According to the Standard
tstamp	Measurement timestamp.	Encoded in the same format as the 64-bit timestamp format as defined in clause 6 of IETF RFC 5905 [13].
ngran_node	ID of the gNB node (gNB CU or DU).
mcc, mnc	Mobile Country Code and Mobile Network Code.	Mobile Country Code & Mobile Network Code
mnc_digit_len	Number of digits in the MNC (e.g., 2 or 3).
nb_id, cu_du_id	ID of the base station node (gNB), or of the CU.
len_slices	Total number of defined slices.
sched_name	Name of the scheduler in use.	Name of available Scheduler
id	Slice ID.
label, type, type_conf	Slice labels and type configuration.
sched	Scheduling algorithm (e.g., RR, PF).
type_param*	Slice type parameters (e.g., minimum/maximum bandwidth).

• Labels and metadata associated to KPM Measures

Field	My Description (old)	According to the Standard
tstamp	Measurement timestamp.
ngran_node	ID of the gNB node (gNB CU or DU).	Global NG-RAN Node ID This IE is used to globally identify an NG-RAN node in gNB and ng-eNB cases only.
mcc, mnc	Mobile Country Code and Mobile Network Code.	Mobile Country Code & Mobile Network Code
mnc_digit_len	Number of digits in the MNC (e.g., 2 or 3).
nb_id, cu_du_id	ID of the base station node (gNB) or the CU/DU.	This IE uniquely identifies the gNB-CU-UP at least within a gNB-CU-CP. This IE uniquely identifies the gNB-DU at least within a gNB-CU.
MeasType	Type of metric (e.g., throughput, latency).
noLabel		Indicates the associated measurement type without any subcounter. If included, other IEs in 8.3.11 shall not be included in the same Measurement Label (and vice versa).
plmnID, sST, sD	Slice identification.	PLMN Identity Represents the SNSSAI subcounter. OCTET STRING of length 1 indicates SST only. OCTET STRING of length 4 indicates SST + SD. OCTET STRING of length 4 with last 3 bytes as 0xFFFFFF indicates S-NSSAI without SD explicitly. See 3GPP TS 23.003 [20] clause 28.4.2.
fiveQI, qFI, qCI, aRP*, bitrateRange, etc.	QoS parameters associated with the flow.	This IE is used to indicate 5QI value. This IE is used to indicate QCI value. QoS Flow Identifier (QFI): identifies a QoS flow within a PDU Session.
layerMU_MIMO	Number of MIMO layers in use.	Layer at MU-MIMO — Represents the MIMO layer subcounter.
sUM		Sum — Calculated as cumulative sum from the start of the measurement.
distBinX	UE distance to gNB in the X axis.	Distribution Bin X — An index of Bin X. Only applicable to distribution-type measurement information.
distBinY	UE distance to gNB in the Y axis.	Distribution Bin Y — May be present only when Bin X is present.
distBinZ	UE distance to gNB in the Z axis.	Distribution Bin Z — May be present only when Bin X and Bin Y are present.
preLabelOverride	Label override indicator from previous processing.	Precedent Label Override Indication — Indicates that subcounters and their values of the previous label apply, except for newly included subcounters.
startEndInd	Start/end indicator of measurement period.	Indicates a range of values. When used with Distribution Bin subcounters, it indicates multi-dimensional ranges in ascending order: Bin Z → Bin Y → Bin X. When used otherwise, it indicates a one-dimensional range and the “start” and “end” labels must only differ in that one subcounter.
min	Minimum value of the metric observed during the interval.	Minimum of the measured values over a granularity period.
max	Maximum value of the metric observed during the interval.	Maximum of the measured values over a granularity period.
avg	Average value of the metric observed during the interval.	Average of the measured values over a granularity period.

• MAC p/UE metrics

Field	My Description (old)	According to the Standard
tstamp	Measurement timestamp.	Encoded in the same format as the 64-bit timestamp format as defined in clause 6 of IETF RFC 5905 [13].
ngran_node	ID of the gNB node (gNB CU or DU).
mcc, mnc	Mobile Country Code and Mobile Network Code.	Mobile Country Code & Mobile Network Code
mnc_digit_len	Number of digits in the MNC (e.g., 2 or 3).
nb_id	ID of the base station node (gNB) or of the CU/DU.
cu_du_id	Textual identifier of the CU/DU.
frame	Frame number where the measurement was taken.
slot	Slot number within the corresponding frame.
dl_aggr_tbs	Downlink aggregated transport block size.
ul_aggr_tbs	Uplink aggregated transport block size.
dl_aggr_bytes_sdus	Downlink aggregate bytes of SDUs.	Downlink aggregated amount of MAC SDU bytes.
ul_aggr_bytes_sdus	Uplink aggregate bytes of SDUs.	Uplink aggregated amount of MAC SDU bytes.
dl_curr_tbs	Current transport block size in downlink.
ul_curr_tbs	Current transport block size in uplink.
dl_sched_rb	Number of scheduled resource blocks in downlink.
ul_sched_rb	Number of scheduled resource blocks in uplink.
pusch_snr	SNR measured on uplink (PUSCH).
pucch_snr	SNR measured on uplink (PUCCH).
rnti	UE ID (Radio Network Temporary Identifier).	This represents a temporary UE Identifier in a cell in a Radio Network.
dl_aggr_prb	Total number of PRBs used in DL.
ul_aggr_prb	Total number of PRBs used in UL.
dl_aggr_sdus	Total number of SDUs transmitted in DL.	Downlink aggregate MAC SDU — This measurement provides the transmitted data volume in the downlink during a measurement period.
ul_aggr_sdus	Total number of SDUs transmitted in UL.	Uplink aggregate MAC SDU — This measurement provides the transmitted data volume in the uplink during a measurement period.
dl_aggr_retx_prb	PRBs used for HARQ retransmissions in DL.
ul_aggr_retx_prb	PRBs used for HARQ retransmissions in UL.
wb_cqi	Average wideband Channel Quality Indicator.
dl_mcs1	Modulation and Coding Scheme used in the first DL stream.
ul_mcs1	MCS used in the first UL stream.
dl_mcs2	MCS used in the second DL stream (if applicable).
ul_mcs2	MCS used in the second UL stream (if applicable).
phr	Power Headroom.
bsr	Buffer Status Report.
dl_bler	Downlink Block Error Rate.
ul_bler	Uplink Block Error Rate.
dl_num_harq	Total number of HARQ transmissions in DL.
dl_harq_round0	DL transmissions completed on first attempt.
dl_harq_round1	DL transmissions requiring 1 retransmission.
dl_harq_round2	DL transmissions requiring 2 retransmissions.
dl_harq_round3	DL transmissions requiring 3 retransmissions.
dlsch_errors	Number of DLSCH decoding failures.
ul_num_harq	Total number of HARQ transmissions in UL.
ul_harq_round0	UL transmissions completed on first attempt.
ul_harq_round1	UL transmissions with 1 retransmission.
ul_harq_round2	UL transmissions with 2 retransmissions.
ul_harq_round3	UL transmissions with 3 retransmissions.
ulsch_errors	HARQ and retransmission statistics (UL).

• Metrics of RLC layer per carrier

Field	My Description (old)	According to the Standard
tstamp	Measurement timestamp.	Encoded in the same format as the 64-bit timestamp format as defined in clause 6 of IETF RFC 5905 [13].
ngran_node	ID of the gNB node (gNB CU or DU).
mcc, mnc	Mobile Country Code and Mobile Network Code.	Mobile Country Code & Mobile Network Code
mnc_digit_len	Number of digits in the MNC (e.g., 2 or 3).
nb_id	ID of the base station node (gNB).
cu_du_id	Textual identifier of the CU/DU.
txpdu_pkts	Transmitted data packets (PDUs).	Aggregated number of transmitted RLC PDUs
txpdu_bytes	Transmitted data volume (PDU bytes).	Aggregated amount of transmitted bytes in RLC PDUs
txpdu_wt_ms	Average waiting time (ms) before transmission.	Aggregated head-of-line TX packet waiting time to be transmitted (i.e., sent to the MAC layer)
txpdu_dd_pkts	Number of PDUs discarded before transmission.	Number of discarded or dropped PDU packets transmitted
txpdu_dd_bytes	Volume of discarded PDU bytes before transmission.	Amount of discarded or dropped PDU bytes
txpdu_retx_pkts	Number of retransmitted PDUs.	Number of retransmitted PDU packets
txpdu_retx_bytes	Volume of retransmitted PDU bytes.	Amount of retransmitted PDU bytes
txpdu_segmented	Number of PDUs segmented for transmission.	Aggregated number of segmentations
txpdu_status_pkts	Number of RLC status PDUs transmitted.	Aggregated number of TX status PDUs (only applicable to RLC AM)
txpdu_status_bytes	Volume of status PDU bytes transmitted.	Aggregated amount of TX status bytes (only applicable to RLC AM)
txbuf_occ_bytes	Current TX buffer occupancy (bytes).	Transmitting bytes currently in buffer
txbuf_occ_pkts	Number of packets in TX buffer.	Current TX buffer occupancy in terms of number of packets
rxpdu_bytes	Total PDU bytes received.	Number of received bytes in RLC PDUs
rxpdu_pkts	Total PDUs received.	Amount of received RLC PDU packets
rxpdu_dup_pkts	Number of duplicated PDUs received.	Aggregated number of duplicated packets
rxpdu_dup_bytes	Volume of duplicated PDU bytes received.	Aggregated number of RX duplicated bytes
rxpdu_dd_pkts	Number of PDUs discarded after reception.	Aggregated number of RX packets dropped or discarded by the RLC
rxpdu_dd_bytes	Volume of discarded PDU bytes after reception.	Aggregated amount of RX bytes dropped or discarded by the RLC
rxpdu_ow_pkts	Number of out-of-window PDUs received.	Aggregated number of out-of-window received RLC PDUs
rxpdu_ow_bytes	Volume of out-of-window PDU bytes.	Aggregated number of out-of-window bytes received in RLC PDUs
rxpdu_status_pkts	Number of status PDUs received.	Aggregated number of RX status PDUs (only applicable to RLC AM)
rxpdu_status_bytes	Volume of status PDU bytes received.	Aggregated number of RX status bytes (only applicable to RLC AM)
rxbuf_occ_bytes	Current RX buffer occupancy (bytes).	Received bytes currently in buffer
rxbuf_occ_pkts	Number of packets in RX buffer.	Current RX buffer occupancy in terms of number of packets
txsdu_pkts	Number of SDUs delivered for transmission.	Number of SDU packets delivered
txsdu_bytes	Volume of transmitted SDU bytes.	Number of SDU bytes successfully transmitted so far (counter)
txsdu_avg_time_to_tx	Average time from SDU to transmission.	100ms-windowed per packet sojourn time (SDU to PDU) in microseconds
txsdu_wt_us	Total waiting time of SDUs in TX buffer (µs).	Head-of-line (HOL) delay of the current radio bearer, in microseconds
rxsdu_pkts	Number of SDUs delivered to upper layer after reception.	Number of SDU packets received
rxsdu_bytes	Volume of SDU bytes delivered to upper layer.	Number of SDU bytes successfully received so far (counter)
rxsdu_dd_pkts	Number of SDUs discarded after reception.	Number of received discarded or dropped SDU packets
rxsdu_dd_bytes	Volume of SDU bytes discarded.	Number of SDU bytes discarded or dropped
rnti	UE ID (Radio Network Temporary Identifier).	This represents a temporary UE Identifier in a cell in a Radio Network.
mode	Mode (AM, UM, etc.).	0: RLC AM; 1: RLC UM; 2: RLC TM
rbid	Radio Bearer ID.	Radio Bearer Identification — refers to the unique identification assigned to each radio bearer in the network

• UE association to network slices measures

Field	My Description (old)	According to the Standard
tstamp	Measurement timestamp.	Encoded in the same format as the 64-bit timestamp format as defined in clause 6 of IETF RFC 5905 [13].
ngran_node	ID of the gNB node (gNB CU or DU).
mcc, mnc	Mobile Country Code and Mobile Network Code.	Mobile Country Code, Mobile Network Code
mnc_digit_len	Number of digits in the MNC (e.g., 2 or 3).
nb_id, cu_du_id	ID of the base station node (gNB) or the CU.
len_ue_slice	Number of slices assigned to the UE.
rnti	UE ID (Radio Network Temporary Identifier).	This represents a temporary UE Identifier in a cell in a Radio Network.
dl_id	Slice ID in downlink.

💡 All documentation was done through the standards below, as well as comments found directly in the variable definitions.

E2 General Aspects and principles V2

• O-RAN.WG3.E2GAP-v02.00

E2 Service Models - Key Performance Metrics

• E2SM-KPM v2.01
• E2SM-KPM v2.03
• E2SM-KPM v3.00

E2 Service Models - Ran Control:

• O-RAN E2 Service Model (E2SM), RAN Control 1.03

E2 Application Protocol - Technical Specification:

• O-RAN.WG3.TS.E2AP-R004-v07.00

3GPP Reference for the KPM measurement names:

• TS 32.425
• TS 28.552